Angiogenesis is a biological process that provides tissues or organs with new blood vessels, and, in particular, refers to the growth of new capillaries from existing micro-vessels and is a fundamental process in which blood vessels are formed in the body after growth. The angiogenic process is very complicated and elaborate, and is briefly described as follows. First, when a stimulus for angiogenesis is transmitted to existing blood vessels, the blood vessels are expanded and membrane permeability thereof is increased. Second, fibrin is released to the outside of the expanded blood vessels to be deposited in a cytoplasmic matrix around the blood vessels. Third, enzymes for degrading a basement membrane of the existing blood vessels are activated, the basement membrane is destroyed, and endothelial cells are released from the blood vessels via the destroyed basement membrane and proliferate in the matrix of neighboring cells and migrate. Lastly, endothelial cells arranged in a row form blood vessels, thereby completing angiogenesis.
The angiogenic process is strictly regulated by various negative and positive regulators. When angiogenesis is abnormally regulated, various diseases such as cancer, rheumatoid arthritis, diabetic retinopathy, and the like occur. In particular, in a case in which this pathological angiogenesis occurs in the retina, the angiogenesis causes retinal edema, a retinal or vitreous hemorrhage, and retinal detachment. In addition, angiogenesis in the retina becomes a major cause of retinopathy of prematurity, diabetic retinopathy, and senile macular degeneration.
Meanwhile, nanoparticles (NPs) have been widely used for industrial and biomedical purposes. In particular, the NPs have been used as a promising material in biomedical fields such as drug delivery, gene delivery, intracellular imaging, and phototherapy, and, particularly, gold or silica nanomaterials have attracted much attention due to ease of synthesis and action, chemical stability, biocompatibility, and adjustable optical and electrical properties thereof.
Recently, gold or silver NPs have been known to inhibit vascular endothelial growth factor (VEGF)-induced angiogenesis, and studies on the development of angiogenesis inhibitors using the same have been conducted. However, to use the NPs in treatment, careful evaluation of the toxicity of NPs and efforts to minimize the toxicity are required.